Project Summary/Abstract The central role of amyloid beta peptide (A?) in Alzheimer's Disease (AD) has been established by more than a decade of genetic, biochemical, animal, and human studies, but the biological functions of A? and the role of A? production and clearance in A? aggregation and in tau aggregation remain very unclear. The studies proposed in this PPG bring together three Project leaders with distinct and complementary experimental approaches to these questions. These studies will address the role of the sleep-wake cycle and brain network activity in modulating A? and tau aggregation and will also assess the effect of A? on tau spreading. These studies will further assess how the apoE/LRP1/HSPG pathways influence these effects. These studies will use a variety of tools to manipulate gene expression, including transgenic mice and lentiviral (LV) and adeno- associated virus (AAV) vectors. Viiral vectors, in combination with use of animal models that have selective expression of Cre recombinase and with Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) and possibly with optogenetics, will allow both temporal and spatial control of manipulation of gene expression. Viral vectors are required for experiments in the intact CNS, where DNA transfection techniques are ineffective and generation of transgenic animals requires great time and expense. The Viral Vectors Core will design and produce these vectors, a more efficient approach than generating these vectors in individual labs. The Core has provided both LV and AAV vectors to the Washington University neuroscience community and to many groups outside our University for the past 11 years, with vectors provided for more than 100 different labs. The Core has experience with RNA silencing using shRNAs in both LV and AAV vector formats. The Core has developed new vectors to allow genetic manipulation of specific cell types and has packaged vectors for both DREADDS and optogenetics applications. The Core will work with Project 1-3 PIs to produce AAV vectors and LV vectors. The Core will use cultured neurons to test vectors to ensure the highest chance of success in more difficult and time-consuming in vivo experiments. The Core will work with PIs to devise new approaches and vectors as needed as experimental demands evolve.